1. Field
The present invention relates to a system and method for improving the vehicle feel, fuel efficiency and performance of a hybrid vehicle.
2. Description of the Related Art
A hybrid vehicle (HV) has an internal combustion engine and an electric motor that are each used to power the vehicle. The HV also has an energy storage device that provides power to the electric motor and is typically recharged using regenerative braking. A plug-in hybrid vehicle (PHV) also has an internal combustion engine and an electric motor that are each used to power the vehicle. The PHV has a built-in energy storage device that allows it to be charged using an external power source (e.g., a power supply at a charging station). A fuel cell vehicle (FCV) or a fuel cell electric vehicle (FCEV) uses a fuel cell to power its on-board electric motor. Fuel cells in vehicles create electricity to power an electric motor, generally using oxygen from the air and hydrogen. The term “vehicle” and “hybrid vehicle” will be used herein to refer to these types of vehicles.
Hybrid vehicles have an electric vehicle (EV) driving mode and a hybrid vehicle (HV) driving mode. The EV driving mode means that only the electric motor is used to power the hybrid vehicle. The HV driving mode means that only the internal combustion engine or the fuel cell is used to power the hybrid vehicle. Generally, the EV driving mode provides a more responsive feel than the HV driving mode.
In order to achieve a desired fuel efficiency or vehicle performance, an electronic control unit (ECU) is used to automatically switch from the EV driving mode to the FIV driving mode and vice versa. Currently, ECUs use complicated rules and logic algorithms (not dependent on the state of charge) to determine whether to transition from one driving mode to another driving mode. The ECUs perform these calculations and automatically determine whether to switch from one driving mode to another driving mode. Sometimes when the ECUs switch from one driving mode to another driving mode, the timing is not always predictable and the transition is not well defined and not very smooth. Also, with the currently used rules and logic algorithms, the EV driving mode does not provide the driver with a smooth and responsive feel.
Thus, there is a need for hybrid vehicles that provide better transitions and more predictable timing between EV and HV driving modes, provide better fuel economy and efficiency and provide an improved vehicle feel between EV and HV driving modes that is logical and predictable.